/**
 * 通过 apply() 或 call() 改变 this 指向的特性，实现实例成员的继承
 */
function Parent(instanceAttr) {
  this.instanceAttr = instanceAttr
  this.instanceFn = function () {
    console.log('instanceFn')
  }
}

function Child() {
  Parent.apply(this, arguments)
}

var child = new Child('instanceAttr')
console.log(child.instanceAttr)
child.instanceFn()
